How can I implement async validation in Formik?

How can I implement async validation in Formik?

You can implement async validation in Formik by using the validate function or the validationSchema prop with Yup.

Can you show me an example of using Yup for async validation?

Sure! You can create a Yup schema with an async test like this:

import * as Yup from 'yup';

const validationSchema = Yup.object().shape({
  email: Yup.string()
    .email('Invalid email')
    .required('Required')
    .test('checkEmail', 'Email already in use', async (value) => {
      const response = await fetch(`/api/check-email?email=${value}`);
      const data = await response.json();
      return !data.exists;
    }),
});

What if I want to show a loading state while validating?

You can manage a loading state using Formik's setSubmitting method. Set it to true before the async call and false after.

Is there a way to debounce the validation to avoid too many requests?

Yes, you can use a debounce function to delay the validation call. Libraries like lodash provide a debounce function that can help with this.